Effect of different surface treatments on the mechanical properties of monolithic zirconia material

The aim of this study is to investigate the effects of sandblasting and hydrofluoric acid (HF) application as a surface treatment on early and late period of cement bonding, biaxial flexural strength and t-m phase transformation of a current monolithic zirconia material. Disc-shaped (12×1.2 mm) sintered monolithic zirconia samples (XT, VITA YZ, Vita Zahnfabrik, Bad sackingen, Germany) were divided into 5 groups as Group C (sandblasting), Group K20HF (sandblasting+20% HF), Group K40HF (sandblasting+40% HF), Group 20HF (20% HF), Group 40HF (40% HF) then related surface treatments were applied. X-ray differentiation (XRD) and scanning electron microscopy (SEM) analyses were performed on one sample from each group. After the shear bond strength test (SBSt) was applied to seven aged and non-aged samples from all groups, one sample from each group was analyzed with SEM. The data obtained were recorded respectively as SBS1 and SBS2 values. Biaxial flexural strength test (BFSt) was applied to seven aged and non-aged samples, then XRD and SEM analysis were performed on one sample from each of the aged groups. The data obtained were recorded respectively as BFS1 and BFS2 values. Data were evaluated by 2-way analysis of variance (2-way ANOVA), and differences between groups were evaluated by Tukey HSD test. The highest SBS values were recorded for sandblasting (Group C), while the lowest SBS values were recorded for group 40HF, and this difference was significant for non-aged groups (P<0.05). Sandblasting significantly reduced BFS1 and BFS2 values (P<0.05). BFS2 values were higher than BFS1 values (P<0.05). No monoclinic phase was observed before and after artificial aging in any group. No difference was found between SBS values for sandblasting, 20% HF, and 40% HF. Sandblasting reduced the strength of the monolithic zirconia material more than HF application. The HF application can be considered as an alternative surface treatment method to the sandblasting.